Crucial Exams

CompTIA Linux+ XK0-006 (V8) Practice Question

A security audit finds that the executable /usr/local/bin/custombackup is owned by root and has the set-user-ID bit set:

-rwsr-xr-- 1 root users 27829 Jul 31 10:42 /usr/local/bin/custombackup

An ordinary user (UID 1001) launches the program, then inspects its credentials in /proc//status and sees:

Uid:    1001   0   0   0
Gid:     100  100 100 100

(The four values shown for Uid are, in order, the real, effective, saved-set and filesystem user IDs.)

Moments later the program successfully opens /etc/shadow, a file that is readable only by root. Which identifier shown in the Uid line was actually used by the kernel to determine that the process could read that file?

  • The real user ID (value 1001)

  • The real group ID (value 100)

  • The effective user ID (value 0)

  • The saved set-user-ID (value 0)

CompTIA Linux+ XK0-006 (V8)
Services and User Management
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